GB908522A - Gyromagnetic resonance methods and apparatus - Google Patents

Abstract

908,522. Gyromagnetic testing apparatus. VARIAN ASSOCIATES. Dec. 8, 1958 [Dec. 19, 1957], No. 39553/58. Class 37. In gyromagnetic resonance testing apparatus, the means for applying radio frequency energy to a substance to produce gyromagnetic resonance therein and the receiver for detecting electromagnetic signal produced by said resonance are rendered operative alternately, the period of the testing cycle being less than the relaxation time of the substance. In Fig. 1 the substance 11 is located in a coil 13 between the poles of a magnet 12, the field of which is swept over a range by a circuit 18. A pulse-producing circuit 19 causes a transmitter to become operative to induce gyro-resonance in the substance v hereupon the transmitter is rendered inoperative by the pulsing device and the receiver rendered operative so that the continuing resonarce induces a signal in the coil which may be amplified in the receiver and applied to a detector and cathode-ray tube system 17. The testing cycle is so short that the resonance of the sample is phase coherent with the applied frequency. In an alternative arrangement (Fig. 2, not shown), the transmitter and receiver are connected to separate coils which are arranged at right-angles adjacent the substance while in a further embodiment (Fig. 6, not shown) a phase-sensitive detector is used. In another embodiment, for detecting paramagnetic resonance, the substance is located in a cavity resonator and the receiver comprises a crystal mixer and local oscillator arrangement, the receiver being rendered inoperative by switching the local oscillator or an amplifier following the mixer. The detector in Figs. 1-6 may be an envelope detector but may be arranged to show the original oscillations by mixing, in a phase-sensitive detector, an unpulsed output from the transmitter with the received signal.